JP2009115198A - Fixed type constant velocity universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase elastic pressing force applied to a ball without changing design of one compression coil spring by a simple means. <P>SOLUTION: The fixed type constant velocity universal joint has an outer ring 10 forming a plurality of track grooves 14 extending in the axial direction, an inner ring 20 forming a plurality of track grooves 24 making a pair with the track grooves 14 of the outer ring 10, a torque transmission ball 30 arranged in a wedge-shaped ball track formed by cooperation between the track grooves 14 of the outer ring 10 and the track grooves 24 of the inner ring 20, and a cage 40 arranged between a spherical surface-shaped inner peripheral surface 12 of the outer ring 10 and a spherical surface-shaped outer peripheral surface 22 of the inner ring 20 and holding the ball 30, and is constituted so that a pressing part 53 is arranged in the inner ring 20, and a receiving part 56 receiving the elastic pressing force from its pressing part 53 is arranged in the case 40, and the inner ring 20 is displaced in the axial direction toward the diametrically expanding side of the ball track. A means for applying the elastic pressing force to the pressing part 53 is formed as a parallel double structure composed of a first coil spring 54a and a second coil spring 54b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixed type constant velocity universal joint, and more particularly to a fixed type constant velocity universal joint incorporated in a steering device of an automobile.

  Constant velocity universal joints are broadly classified into fixed types that allow only angular displacement between the input and output shafts, and sliding types that allow angular displacement and axial displacement. Each model is selected according to the application and usage conditions. The As a fixed type constant velocity universal joint, a Rzeppa type (hereinafter referred to as “BJ”) and an undercut free type (hereinafter referred to as “UJ”) are widely known.

  Both BJ and UJ have an outer ring in which a plurality of track grooves extending in the axial direction are formed on the inner spherical surface, and an inner ring in which a plurality of track grooves extending in the axial direction in pairs with the track grooves of the outer ring are formed in the outer spherical surface. And a torque transmitting ball incorporated between the track groove of the outer ring and the track groove of the inner ring, and a cage for holding the ball constitute a main part.

  The outer ring track groove center is located on the outer ring opening side with respect to the inner spherical center, and the inner ring track groove center is located on the outer ring rear side with respect to the outer spherical center, and is offset by an equal distance in the opposite direction in the axial direction. (Track offset).

  Thereby, the ball track constituted by the track groove of the outer ring and the track groove of the inner ring has a wedge shape that expands toward the opening side of the outer ring. In BJ, the entire area of each track groove is curved, whereas in UJ, one end of each track groove is in a straight shape parallel to the axis.

  Generally, two or more cardan joints are used for a shaft joint incorporated in an automobile steering device. Since this joint is not uniform at a single unit, it is arranged and used so as to cancel each other's fluctuation components in order to ensure constant velocity.

  For this reason, there exists a problem that the design freedom of a vehicle is impaired. By using a constant velocity universal joint that can ensure constant velocity at an arbitrary angle as a steering shaft joint, it is possible to increase the design freedom of the vehicle, but the constant velocity universal joint has a large amount of play in the rotation direction, There is concern that the steering operation feeling in the vicinity of the vehicle going straight may be deteriorated or abnormal noise may be caused.

  In order to solve this, it has been proposed to provide a preload means inside the constant velocity universal joint to close the track groove clearance (see, for example, Patent Document 1).

  The fixed type constant velocity universal joint has a gap between the outer ring track groove and the inner ring track groove due to the function and machining surface, and the inner ring outer sphere, cage outer sphere, inner ring outer sphere There is also a clearance on the inner spherical surface of the cage.

  These clearances are the amount of movement when either the inner ring or the outer ring is fixed in the neutral state of the joint and the other is moved in the radial direction or axial direction. Depending on the direction of movement, radial clearance, axial clearance, etc. be called.

These clearances greatly affect the circumferential play (rotational backlash) between the inner and outer rings, and the larger the track groove clearance, the greater the rotational backlash. For this reason, a rotational backlash exceeding a certain level is unavoidable. Therefore, this type of fixed constant velocity universal joint is generally employed for applications that hate rotational backlash, such as a steering device of an automobile. Has not reached.
Japanese Patent Laid-Open No. 2003-130082 JP 2005-221032 A

  By the way, a fixed type constant velocity universal joint has been proposed which aims to improve the feeling characteristics by eliminating the circumferential clearance (rotational backlash) between the inner and outer rings described above (see, for example, Patent Document 2). ).

  In this constant velocity universal joint, a case is attached to the inner end of the shaft that is spline-fitted to the inner ring, a ball is accommodated inside the case via a compression coil spring, and the ball protrudes from the case opening. I am letting. On the other hand, a concave spherical receiving member is attached to the rear end portion of the cage, and the inner ring side ball is brought into contact with the cage side receiving member.

  By receiving the elastic pressing force from the ball by the compression coil spring with the member, the inner ring is displaced in the axial direction toward the diameter-enlarged side of the ball track, so that the rotational backlash is reduced.

  Here, in order to reliably eliminate the rotation backlash, the elastic force of the compression coil spring may be increased, but there is a limit to the design for increasing the elastic force of one compression coil spring. That is, as a design for increasing the elastic force of the compression coil spring, there are means for increasing the wire diameter of the coil spring, decreasing the coil diameter, or increasing the free length.

  However, even if any of these means is adopted, it may be difficult to reliably eliminate the rotational backlash by the elastic force of one compression coil spring, and the torsion angle-torque characteristic of the constant velocity universal joint That is, it may be difficult to increase the torsional rigidity in some cases.

  Therefore, the present invention has been proposed in view of the above-described problems, and the object of the present invention is to provide an elastic pressing force applied to the ball without any design change of one compression coil spring by a simple means. The object is to provide a fixed type constant velocity universal joint which can be enlarged.

  As a technical means for achieving the above-mentioned object, the present invention provides an outer member having a spherical inner peripheral surface formed with a plurality of track grooves extending in the axial direction, and a pair of track grooves of the outer member. An inner member having a spherical outer peripheral surface formed with a plurality of axially extending track grooves, and a wedge-shaped ball formed by the cooperation of the outer member track grooves and the inner member track grooves A torque transmitting ball disposed on the track; and a cage disposed between the spherical inner peripheral surface of the outer member and the spherical outer peripheral surface of the inner member for holding the ball, and pressing the inner member The cage is provided with a receiving portion that receives elastic pressing force from the pressing portion, and the elastic member receives the elastic pressing force from the pressing portion, so that the inner member is directed toward the diameter expansion side of the ball track. For fixed type constant velocity universal joints Means for imparting elastic pressing force to the pressing unit, characterized in that a parallel dual structure of the coil spring. Here, “a parallel double structure of coil springs” means a structure in which two coil springs are arranged in parallel.

  In the fixed type constant velocity universal joint according to the present invention, the means for applying the elastic pressing force to the pressing portion has a parallel double structure of the coil spring, so that the pressing portion can be changed without changing the design of one coil spring itself. It is possible to increase the elastic pressing force applied to. As a result, the rotational backlash can be eliminated more reliably, and the torsion angle-torque characteristic of the constant velocity universal joint, that is, the torsional rigidity can be easily increased.

  In the present invention, the pressing portion includes a case attached to the end of the inner member, a coil spring housed in the case, and a ball that is disposed at the tip of the coil spring and protrudes from the case opening. It is desirable to provide a structure in which the elastic pressing force of the coil spring is biased in the ball protruding direction. In the case of such a structure, a parallel double structure of coil springs is realized by housing two coil springs inside the case.

  When the coil spring is accommodated in the case, a structure in which a restricting portion for positioning the base end portion of the coil spring is formed on the case bottom portion where the base end portion of the coil spring contacts is desirable. In this way, the position of the coil spring can be stabilized by positioning the proximal end portion of the coil spring by the restricting portion formed on the bottom of the case, and the elastic pressing force of the coil spring can be It becomes easy to positively bias in the protruding direction.

  In addition, when two coil springs are accommodated inside the case, the parallel double structure of the coil springs is arranged on the inner side of the first coil spring and the first coil spring, and the first coil spring diameter What is necessary is just to comprise with the 2nd coil spring which has a smaller diameter. If it does in this way, the 1st coil spring and the 2nd coil spring can be effectively arranged in the limited space inside the case.

  In the parallel double structure of the coil spring in the present invention, a structure in which the free length of the second coil spring is longer than that of the first coil spring is desirable. If it does in this way, the elastic pressing force of the 2nd coil spring arrange | positioned at the internal-diameter side of the 1st coil spring can be made to act on a ball | bowl reliably. That is, since the ball to which the elastic pressing force is applied has a spherical shape, if the free length of the second coil spring located on the inner diameter side of the first coil spring is made longer than that of the first coil spring, The tip of the second coil spring can be reliably brought into contact with the ball.

  When the fixed type constant velocity universal joint described above is incorporated in a steering apparatus of an automobile, the track groove clearance in the constant velocity universal joint is filled to prevent rotation backlash, and thus a more remarkable effect is exhibited. The automobile steering apparatus may be an electric power steering apparatus that applies a steering assist force by a motor, or may be a hydraulic power steering apparatus.

  According to the present invention, since the means for applying an elastic pressing force to the pressing portion has a parallel double structure of coil springs, the elastic force applied to the pressing portion without changing the design of one coil spring itself. The pressing force can be increased. As a result, the rotational backlash can be eliminated more reliably, and the torsion angle-torque characteristic of the constant velocity universal joint, that is, the torsional rigidity can be easily increased.

  When this fixed type constant velocity universal joint is incorporated in the steering system of an automobile, it is possible to improve the feeling of steering operation in the vicinity of straight ahead of the vehicle and improve the feeling characteristics, and high quality fixed type that does not generate abnormal noise. A constant velocity universal joint can be provided.

  An embodiment of a fixed type constant velocity universal joint according to the present invention will be described in detail. In the following embodiment, a case where the present invention is applied to a Rzeppa type (BJ) which is a kind of a fixed constant velocity universal joint for steering is illustrated, but the present invention is not limited to this, and an undercut free type (UJ) It is also applicable to. Further, the fixed type constant velocity universal joint of the present invention is not limited to steering, but can be used for a drive shaft or a propeller shaft.

  First, a steering device incorporating a fixed type constant velocity universal joint will be briefly described. As shown in FIGS. 4A to 4C, the steering device transmits the rotational motion of the steering wheel 6 to the steering gear 8 via a steering column including one or a plurality of steering shafts 2, thereby allowing the tie rod 9. It is made to convert into the reciprocating motion.

  If the steering shaft 2 cannot be arranged in a straight line in consideration of the vehicle-mounted space, etc., one or more shaft couplings 1 are arranged between the steering shafts 2 and the steering gear 8 can be rotated accurately even when the steering shaft 2 is bent. It is possible to transmit exercise. A fixed type constant velocity universal joint is used for the shaft joint 1. The symbol α in FIG. 4B represents the operating angle of the joint, and a large angle in which the operating angle α exceeds 30 ° can be set.

  Next, the fixed type constant velocity universal joint will be described. The fixed type constant velocity universal joint 1 of this embodiment is a Rzeppa type joint (BJ). As shown in FIG. 1, an outer ring 10 as an outer member, an inner ring 20 and a shaft 2 constituting the inner member, and torque are supplied. The transmitting ball 30 and the cage 40 that holds the ball 30 are formed as main components. The outer ring 10 is connected to the input shaft or the output shaft, and the inner ring 20 is connected to the output shaft or the input shaft. In this embodiment, the inner member is configured by coupling the shaft 2 to the inner circumference of the inner ring 20 via torque transmission means such as serrations and splines.

  The outer ring 10 has a cup shape opened at one end, and a plurality of track grooves 14 extending in the axial direction are formed at equal positions in the circumferential direction of the spherical inner peripheral surface 12. The inner ring 20 has a plurality of track grooves 24 extending in the axial direction at equal circumferential positions on the spherical outer peripheral surface 22. The track groove 14 of the outer ring 10 and the track groove 24 of the inner ring 20 are paired to form a ball track, and one ball 30 is incorporated in each ball track. The cage 40 is slidably interposed between the spherical inner peripheral surface 12 of the outer ring 10 and the spherical outer peripheral surface 22 of the inner ring 20, and each ball 30 is accommodated in a pocket 46 of the cage 40 and is circumferentially equivalent. Held at intervals.

The outer peripheral surface 42 of the cage 40 is spherically fitted to the spherical inner peripheral surface 12 of the outer ring 10, and the inner peripheral surface 44 of the cage 40 is spherically fitted to the spherical outer peripheral surface 22 of the inner ring 20. The center of the spherical inner peripheral surface 12 of the outer ring 10 and the center of the spherical outer peripheral surface 22 of the inner ring 20 coincide with the joint center O. On the other hand, the center of curvature O ₁ of the track groove 14 of the outer ring 10 and the center of curvature O ₂ of the track groove 24 of the inner ring 20 are offset by an equal distance in the opposite directions in the axial direction. Therefore, the ball track formed by the pair of track grooves 14 and 24 has a wedge shape that expands from the back side of the outer ring 10 toward the opening side.

  In this fixed type constant velocity universal joint, the ball 30 guided to the cage 40 is always maintained in a plane perpendicular to the bisector of the operating angle regardless of the operating angle of the outer ring 10 and the inner ring 20. The constant velocity of the joint is ensured.

  In this fixed type constant velocity universal joint, a plunger unit 50 is attached to the shaft end 2b of the shaft 2 as shown in FIG. The plunger unit 50 includes a ball 53 as a pressing portion, a first compression coil spring 54a and a second compression coil spring 54b as means for applying an elastic pressing force to the ball 53, a ball 53, and two It is an assembly body which consists of case 55 which accommodates compression coil springs 54a and 54b.

  In this plunger unit 50, the ball 53 protrudes from the opening 55a of the case 55 press-fitted into the recessed hole 2a of the shaft end 2b of the shaft 2, and the first compression coil spring 54a and the second compression coil spring 54b The elastic pressing force is urged toward the back side (ball protruding direction) of the outer ring 10.

  FIG. 2 is a partially enlarged view of FIG. 1 and shows the plunger unit 50 attached to the shaft end 2 b of the shaft 2. The parallel double structure of the compression coil springs in the plunger unit 50 has a configuration in which a first compression coil spring 54a and a second compression coil spring 54b are arranged in parallel.

  That is, the first compression coil spring 54a and the second compression coil spring 54b are accommodated in the case 55, and the second compression coil spring 54b is disposed on the inner diameter side of the first compression coil spring 54a. It has a diameter smaller than the first compression coil spring diameter.

  As described above, if the large-diameter first compression coil spring 54a and the small-diameter second compression coil spring 54b are accommodated in the case 55 in a concentric arrangement, the first space is limited in the restricted space inside the case 55. The compression coil spring 54a and the second compression coil spring 54b can be effectively disposed.

  In the structure in which the first compression coil spring 54a and the second compression coil spring 54b are accommodated inside the case 55, the first compression coil spring 54a and the second compression coil spring 54a are compressed as shown in FIGS. A restricting portion 51 for positioning the base end portions of the first compression coil spring 54a and the second compression coil spring 54b is formed on the bottom portion 55b of the case 55 that contacts the base end portion of the coil spring 54b.

  Examples of the restricting portion 51 include a structure in which the bottom portion 55b of the case 55 is formed into a corrugated cross section. The first compression coil spring 54a is positioned between the inner peripheral wall surface of the case 55 and the annular convex portion 51a formed on the bottom surface, and between the annular convex portion 51a and the central convex portion 51b formed on the bottom surface. The second compression coil spring 54b is positioned.

  Thus, by providing the regulating part 51 on the bottom 55b of the case 55, the first compression coil spring 54a is positioned by positioning the base end parts of the first compression coil spring 54a and the second compression coil spring 54b. And the posture of the second compression coil spring 54b can be stabilized, and the elastic pressing force of the first compression coil spring 54a and the second compression coil spring 54b can be reliably urged in the ball protruding direction. It becomes easy.

Here, as shown in FIG. 3A, the free length of the first compression coil spring 54a located on the outer diameter side is L ₁ , and the free length of the second compression coil spring 54b located on the inner diameter side is L _2. And the free length L ₂ of the second compression coil spring 54b is made longer than the natural length L ₁ of the first compression coil spring 54a (L ₂ > L ₁ ).

In this manner, the elastic pressing force of the second compression coil spring 54b disposed on the inner diameter side of the first compression coil spring 54a can be reliably applied to the ball 53. That is, since the ball 53 to which an elastic pressing force is applied by the first compression coil spring 54a and the second compression coil spring 54b has a spherical shape, the second position located on the inner diameter side of the first compression coil spring 54a. If the free length L ₂ of the compression coil spring 54 b is made longer than the free length L ₁ of the first coil spring 54 a, the tip of the second coil spring 54 b is surely brought into contact with the ball 53.

  On the other hand, as shown in FIG. 1, the cage 40 is provided with a receiving portion 56 that receives an elastic pressing force from the ball 53 of the plunger unit 50. The receiving portion 56 has a partial spherical shape that covers the end opening of the cage 40, and is fixed by press-fitting a peripheral edge thereof into the opening end of the cage 40. The inner surface 56 a (surface facing the shaft 2) of the receiving portion 56 has a concave spherical shape, and the concave spherical inner surface 56 a exhibits a function of receiving an elastic pressing force from the ball 53.

  In the above configuration, when the shaft 2 and the inner ring 20 are serrated and connected together by the retaining ring 4 for preventing the shaft from coming off from the inner ring 20 (see FIG. 1), the ball 53 and the receiving portion of the plunger unit 50 are connected. The inner surface 56a of the concave spherical surface 56 abuts against each other, the ball 53 retracts, and the first compression coil spring 54a and the second compression coil spring 54b are compressed.

  The inner ring 20 integrated with the shaft 2 is axially displaced toward the opening side of the outer ring 10 by the elastic pressing force from the ball 53, and the balls disposed in the track grooves 14 and 24 by the axial displacement of the inner ring 20. 30 and the track grooves 14, 24 abut against each other, so that rotational backlash is reliably prevented.

  Here, in this fixed type constant velocity universal joint, means for applying an elastic pressing force to the ball 53 in the plunger unit 50 is used as a parallel two-unit composed of a first compression coil spring 54a and a second compression coil spring 54b. By adopting the heavy structure, the elastic pressing force applied to the ball 53 as the pressing portion can be increased without changing the design of one coil spring itself. As a result, the rotational backlash can be eliminated more reliably, and the torsion angle-torque characteristic of the constant velocity universal joint, that is, the torsional rigidity can be easily increased.

  The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the gist of the present invention. It includes the equivalent meanings recited in the claims and the equivalents recited in the claims, and all modifications within the scope.

1 is a cross-sectional view showing an overall configuration of a constant velocity universal joint for steering in an embodiment of a fixed type constant velocity universal joint according to the present invention. It is a principal part expanded sectional view which shows the plunger unit with which the shaft shaft end of FIG. 1 was mounted | worn. (A) is sectional drawing which shows the case of a plunger unit of FIG. 2, a 1st compression coil spring, and a 2nd compression coil spring, (b) is an A direction arrow directional view of (a). (A) is a top view of a steering apparatus, (b) is a side view of a steering apparatus, (c) is a perspective view of a steering apparatus.

Explanation of symbols

2 Inner member (shaft)
10 Outer member (outer ring)
12 Spherical inner peripheral surface 14 Track groove of outer member (outer ring) 20 Inner member (inner ring)
22 Spherical outer peripheral surface 24 Track groove of inner member (inner ring) 30 Ball 40 Cage 53 Pressing part (ball)
54a First compression coil spring 54b Second compression coil spring 56 Receiving part

Claims (6)

  An outer member having a spherical inner peripheral surface formed with a plurality of track grooves extending in the axial direction, and a spherical surface formed with a plurality of track grooves extending in the axial direction in pairs with the track grooves of the outer member An inner member having an outer peripheral surface, a torque transmitting ball disposed on a wedge-shaped ball track formed by cooperation of a track groove of the outer member and a track groove of the inner member, and a spherical surface of the outer member A cage arranged between the inner peripheral surface of the inner member and the spherical outer peripheral surface of the inner member to hold the ball, and provided with a pressing portion on the inner member and receiving an elastic pressing force from the pressing portion. In the fixed type constant velocity universal joint that axially displaces the inner member toward the diameter-expanded side of the ball track by providing a receiving portion in the cage and receiving the elastic pressing force from the pressing portion at the receiving portion. A hand for applying an elastic pressing force to the pressing portion. The fixed type constant velocity universal joint, characterized in that it has a parallel double structure of the coil spring.   The pressing portion includes a case attached to an end portion of the inner member, a coil spring housed in the case, and a ball that is arranged at a tip portion of the coil spring and protrudes from the case opening, The fixed constant velocity universal joint according to claim 1, wherein an elastic pressing force of the coil spring is biased in a ball protruding direction.   The fixed type constant velocity universal joint according to claim 1 or 2, wherein a restricting portion for positioning the base end portion of the coil spring is formed at a case bottom portion with which the base end portion of the coil spring contacts.   The parallel double structure of the coil spring includes a first coil spring and a second coil spring disposed on the inner diameter side of the first coil spring and having a diameter smaller than the first coil spring diameter. The fixed type constant velocity universal joint according to any one of claims 1 to 3.   The fixed type constant velocity universal joint according to any one of claims 1 to 4, wherein in the parallel double structure of the coil springs, the free length of the second coil spring is longer than that of the first coil spring.   The fixed constant velocity universal joint according to any one of claims 1 to 5, which is incorporated in a steering device for an automobile.

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